HairNet addon moves other hair systems on same emitter mesh
This bug happens since Blender 2.9 and HairNet 0.6.2 were released. The hair particles of one of the existing hair particle systems move down along the z-axis for some reason when another hair particle system is added by HairNet.
You can pull the hair particles up again in comb mode but a better workaround is to disable all existing hair particle systems in the viewport before you add another hair particle system with the addon. After the new one is added you can enable them again.